Various forms of projectors for projecting slides or transparencies are known, for producing cross-bending or mixing of the images. Such a projector may be referred to hereinafter as a mixing projector.
A mixing projector as disclosed for example in German patent specification No. 3,517,376 typically comprises first and second image projector units which are combined together to form an assembly and which each comprise an objective lens, a slide holder and a lighting system. The projector further comprises a guide means for a common slide magazine and a slide change means. In that projector, the guide means for the common magazine conventionally extends in parallel relationship with the optical axes of the optical system including the objective lenses of the image projector units. The respective projector arrangements each comprising the slide carrier and the lighting system are displaceable along the optical axes of the optical systems, to permit a change of slide in the respective projector units.
Now, the displacement required for the respective projector units means that the interior of the projector must include a sapce to permit such movement to take place, and the necessity for that space, which is provided only to permit such movement to occur and does not therefore perform any other useful function, necessarily results in the projector being of correspondingly large size. Furthermore, in a slide change operation, that projector involves the movement of relatively large masses, namely the mass of a projection unit comprising a slide carrier and the lighting system.